The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
The term electroencephalography (EEG) generally refers to the measurement of electrical activity produced by the brain as measured or recorded from electrodes placed on the scalp of a person. The resultant electrical signals from the electrodes are correspondingly termed EEG signals, and are based on the electrical activity within the brain of a person. Such electrical activity is commonly termed “brainwave” activity. A related term, electroencephalogram, refers to a graphic record produced by an EEG.
A system for naming points on the scalp or head where EEG electrodes are attached has been developed. Thus, the International “10-20” system is widely used to describe the location of EEG scalp electrodes for standardization. The 10-20 system is based on the surface placement of the electrode and its relationship to the underlying area of cerebral cortex. The “10” and “20” refer to the actual distances between adjacent electrodes as either 10% or 20% of the total front-back or right-left distance of the skull. Further, the letters F, T, C, P and O, which stand for Frontal, Temporal, Central, Parietal and Occipital, respectively, are used to identify the lobe over which the sensor is placed. A number is further used to identify the hemisphere location. Even numbers (2, 4, 6, 8) refer to electrode positions on the right hemisphere, and odd numbers (1, 3, 5, 7) refer to electrode positions on the left hemisphere.
When using electrodes that are placed on the scalp or head, possibly in accordance with the International “10-20” system, the transmission of the resulting electrical signals corresponding to brainwave activity over wires is referred to telegraph facilitated human-to-human communication over distance. Electrocorticography or intracranial electroencephalography (iEEG) where electrophysiological monitoring of EEG can be performed by placing electrodes directly on the exposed surface of the brain. This, of course, is highly invasive. Such direct brain-to-brain interfaces (BBI) is a modern extension of the early telegraph technology.